Glass optical articles, especially aspheric glass lenses, are widely used in digital cameras, video recorders, compact disc players and other optical systems due to their excellent optical performance. At present, a molding process is commonly used for the manufacturing of glass optical articles. In the molding process, a mold generally is used for molding the glass optical pieces.
In general, molds are exposed to repeated impacts and high temperatures. Thus these molds should have characteristics such as excellent hardness, high heat resistance, high wear resistance, high compressive strength, easy separability, mirror surface workability, etc. A variety of suitable materials may be applied for construction of the mold; for example, grasslike or vitreous carbon, silicon carbide, silicon nitride, and a mixture containing silicon carbide. However, the materials have a common shortcoming; i.e., low thermal shock resistance. In addition, the materials may be easily oxidized due to being subjected to high temperatures in air.
Furthermore, the use of multi-layer coatings covered with the ceramics such as Ti (C, N), Al2O3 on the surface of the carbides is increasing. As a result, some surface characteristics of the molds, for example hardness and wear resistance, may be improved. However, it is generally difficult to tightly adhere the multi-layer coating to a mold matrix due to incompatible properties between different materials. In addition, such a coating also increases the complexity and cost of the molding process.
What is needed, therefore, is a mold that has high chemical stability and high thermal shock resistance under repetitive impact and high temperature operating conditions.
What is also needed, therefore, is a method of manufacturing the above-described mold at low cost.